The hydrogenation of carboxylic acids and carboxylic esters to alcohols is known in the art, and various methods and catalysts have been suggested for effecting the hydrogenation. A commonly practiced method involves the use of a copper-chromite-based hydrogenation catalyst. While copper chromite catalysts are successful and commercially available, the disposal of the spent copper chromite catalyst is a problem since chromium can exist in different oxidation states. Some of these oxidation states are reported to be toxic to humans.
Conversion of detergent range methyl esters or acids to the corresponding alcohols can be carried out at high pressures, i.e., above about 200 bars, or at lower pressures and moderate temperatures in the vapor phase, but the production rates are limited and the processes are economically unattractive. The conversion of methyl esters can also be carried out at lower pressures and moderate temperatures in the liquid phase at high space velocities and low hydrogen to feed ratios, but the process results in the formation of large amounts of wax esters and poor selectivity to the desired alcohol product.
It would therefore be advantageous to have an economically attractive process to hydrogenate detergent range methyl esters to the corresponding alcohols in the liquid phase which would yield an alcohol product of high quality.